package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import com.hmdp.service.impl.ShopServiceImpl;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

@Slf4j
@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithChuanTou(String keyPrefix, ID id, Class<R>type, Function<ID,R> dbFallback,Long time,TimeUnit unit)  {
        String key=keyPrefix+id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在,直接返回
            return JSONUtil.toBean(json,type);
        }
        //判断命中的是否是空值
        if (json != null) {
            //返回一个错误信息
            return null;
        }
        //4.不存在,根据id查询数据库
        R r=dbFallback.apply(id);
        //5.不存在,返回错误
        if (r == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", 2L, TimeUnit.MINUTES);
            return null;
        }
        //6.存在,写入redis,超时剔除
        this.set(key,r,time,unit);
        return r;
    }

    //定义线程池
    private static  final ExecutorService CACHE_REBUILD_EXECUTOR= Executors.newFixedThreadPool(10);
    /**
     * 缓存击穿的示例:利用逻辑过期实现
     */
    public <R,ID> R queryWithLogicalExpire(String keyPrefix,ID id,Class<R>type,Function <ID,R>dbFallback,Long time,TimeUnit unit ) {
        String key=keyPrefix+id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)) {
            //3.存在,直接返回
            return null;
        }
        //4.命中,需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(),type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.1判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //未过期,直接返回店铺信息
            return r;
        }
        //5.2 已过期,需要缓存重建

        //6.缓存重建
        //6.1获取互斥锁
        String lockKey=RedisConstants.LOCK_SHOP_KEY+id;
        boolean isLock=tryLock(lockKey);
        //6.2判断是否获取锁成功
        if(isLock){
            //6.3成功,开启独立线程,实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //重建缓存
                    this.setWithLogicalExpire(key,r1,time,unit);
                }catch (Exception e){
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }

        //6.4 返回过期的商铺信息

        return r;
    }
    //获取锁
    public boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    //释放锁
    public void unLock(String key) {
        stringRedisTemplate.delete(key);
    }
}
